Open topped corrugated cardboard boxes are widely used for the transport, storage and display of fresh produce, especially fresh fruit and vegetables. Such produce is relatively heavy and the boxes need to be capable of being stacked one on top of the other to at least a reasonable height and may entail stacking of from 5 to 10 boxes on top of a lowermost box.
The size of the boxes is targeted at containing a predetermined weight of a predetermined type of fresh produce and may be dictated, at least to some extent, by the size of a pallet on which the boxes are to be transported. Also, as regards their height, the height of a container or other transport vehicle in which they are to be transported will be relevant as well as the general physical size and nature of the type of fresh produce. Many different sizes of boxes are thus manufactured, typically for specific purposes and generally for holding a quantity of a specific type of fruit or vegetable. In any event the objective is to occupy substantially all of the area of a pallet and substantially all of the height of a container or transport vehicle body. Just by way of example, one typical size of a so called citrus box is 594 mm long by 390 mm wide and 169 mm high; one typical size of a so called grape box is 392 mm long by 295 mm wide and 120 mm high; and one typical size of a so called avocado pear box is 360 mm long by 275 mm wide and 90 mm high. Numerous other sizes will be appropriate for other purposes.
Irrespective of the exact size of a box, it is important that the configuration of folds made in a pre-cut and sulcated blank in order to erect a box does not result in any unused space between adjacent boxes. External flaps secured to the outer surfaces of the sides or ends of a box are therefore generally avoided in favour of flaps secured internally to the surfaces of the walls. Also, in order to provide for ventilation and at least a limited amount of inspection of the contents of a box, a major part of the length of the upper edges of the side walls have part of the height, typically about 25 mm, cut away to provide indentations that form openings in vertical stacks of boxes.
Supporting pillars at the corners of a box are created by folding the pre-cut and sulcated sheet material to form what are generally, but not necessarily, triangular pillars. Of course, the strength of a pillar is very much enhanced if the length of the flutes or corrugations extends up the height of the box.
Various different configurations of cuts and folds have been used in the past with different degrees of efficacy and economy of sheet material that is consumed in producing the blanks. The strength of the pillar will, of course, depend on the strength of the sheet material as well as on the cut and direction in which the flutes of various flaps extend.
The cost of a box is therefore very much dependent on the cut and fold configuration of the box, the cost of the sheet material used, and the overall size of the outer periphery of the blank before it is folded.
It is to be mentioned that blanks that are adapted to be manually folded are generally different in that they also have locking tabs and receiving apertures to lock the box in the erected condition. This often leads to extra material being used in order to provide flaps that can be manually locked in position in this manner. Blanks adapted to be manually folded are typically more expensive.
On the other hand blanks that are adapted to be machine folded are generally simply glued in their erected condition. As a general rule the machine folded boxes are preferred if a machine folding facility is available suitably close to the site where the boxes are to be filled as they are generally appreciably less costly. Obviously it is uneconomical from a transport and storage point of view to transport or store any appreciable numbers of erected boxes so that it is usual to transport and store the blanks pending erection for use.
In order to facilitate stacking and vertical alignment of stacked boxes, it is commonplace to provide cut-outs in the lower edge of each of the end walls that register with upstanding tabs forming extensions of the upper edges of the end walls of the next lower box on which a box is being stacked. It is, accordingly, important that the tabs are properly aligned with the cut-outs in the stacked condition and it is not always easy to align such boxes in the event that the upper edges of the end walls are simply cut or folded over edges that are not much more than the thickness of the fluted sheet material being used.
In order to facilitate stacking, the end walls have, in many instances, been provided with an inwardly directed horizontal section termed a ledge so that the bottom of a box can be slid a short distance on the ledges to cause proper registration of the tabs and cut-outs. The ledges typically cover the upper ends of the pillar formations.
In one currently available type of box that has ledges of this nature, the ends of the ledge are extended to provide a side wall attachment flap to be adhesively secured to the inside of the side wall when the box is erected and a second end wall attachment flap secured to the side wall attachment flap by way of a fold. The side walls of the box have attached thereto by way of a fold a first end wall attachment flap the other edge of which has attached thereto, by way of a fold, a pillar forming diagonal flap. This arrangement neatly utilises an exactly rectangular area for the blank with the flutes or corrugations extending longitudinally so that the flutes in the ends of the box extend vertically.
The problem with this arrangement is that the flutes of all of the side wall attachment flap, the second end wall attachment flap (both of which are attached to the ledge), the first end wall attachment flap and pillar forming diagonal flap that are attached to the side wall have the flutes extending horizontally; that is in the weaker of the two directions, at the pillar. This is a natural consequence of the design of the blank of the box and leads to a heavier grade of corrugated cardboard being needed than would otherwise be the case.
It has now surprisingly been found that by reorganising the attachment flaps and ledge it is possible that all of the attachment flaps and any pillar forming diagonal flap can have the flutes extending vertically in the erected condition with consequent enhancement of strength and a potential reduction of cost and strength required of the corrugated cardboard.